1. Field of the Invention
The present invention relates to young leaves of a grass plant such as barley, wheat, rye, oats, adlay, Italian ryegrass, and rice, in which the amount of xcex3-aminobutyric acid having an antihypertensive function contained in the leaves is retained or increased.
2. Description of the Related Art
Green leaves of grass plants, such as the young leaves of barley, wheat, rye, oats, adlay, Italian ryegrass, rice, and the like, are rich in vitamins, minerals, dietary fiber, and so on. They have therefore received attention for their usability as materials for health food products that provide the effects of adsorbing harmful substances, improving the intestinal environment, suppressing absorption of cholesterol, preventing the postprandial sudden rise in blood sugar, activating superoxide dismutase (SOD), and the like. When such young leaves, for example, are used as a material for health foods, they are presented in various forms. For instance, the young leaves of barley are directly dried and powdered to obtain leaf powder (Japanese Patent No. 2544302), or processed into the forms of juice, extract, and powder of such juice and extract (Japanese Laid-Open Patent Publication No. 11-75791). In either case, products having useful ingredients such as dietary fiber and vitamins retained therein in a larger amount is more preferable.
Green grass leaves contain enzymes such as chlorophyllase, peroxidase, and polyphenol oxidase that cause degeneration such as the fading of the vivid green color of green leaves. In order to prevent such degeneration, green leaves are generally subjected to hydrothermal treatment (i.e., blanching). During this treatment, ingredients naturally contained in green leaves, such as vitamins, minerals, and chlorophyll, tend to be lost.
The present inventors have investigated unknown active ingredients contained in green grass leaves, especially young leaves of a grass plant selected from barley, wheat, rye, oats, adlay, Italian ryegrass, and rice, and found that such leaves contain xcex3-aminobutyric acid (hereinafter, may be abbreviated as GABA) that is known as an antihypertensive substance. It has also been found that GABA is conventionally lost during the steps of processing the leaves, for example, at various stages for producing food materials using such young leaves. Therefore, conventionally, a product having a higher amount of GABA cannot be obtained.
The present invention provides young leaves of a grass plant which is at least one selected from the group consisting of barley, wheat, rye, oats, adlay, Italian ryegrass, and rice, containing xcex3-aminobutyric acid in an amount of 500 mg/100 g or more in terms of dry weight.
In a preferred embodiment, the above-mentioned young leaves can be obtained by subjecting harvested young leaves of the grass plant or processed products thereof to at least one treatment selected from the group consisting of incubation treatment, anaerobic treatment, and microwave treatment.
The present invention also provides young leaf powder of a grass plant which is at least one selected from the group consisting of barley, wheat, rye, oats, adlay, Italian ryegrass, and rice, containing xcex3-aminobutyric acid in an amount of 20 mg/100 g or more in terms of dry weight.
In a preferred embodiment, the above-mentioned young leaf powder can be obtained by subjecting harvested young leaves of the grass plant or processed products thereof to at least one treatment selected from the group consisting of incubation treatment, anaerobic treatment, and microwave treatment, and drying and powdering the treated young leaves.
The present invention further provides young leaf juice of a grass plant which is at least one selected from the group consisting of barley, wheat, rye, oats, adlay, Italian ryegrass, and rice containing xcex3-aminobutyric acid in an amount of 800 mg/100 g or more in terms of dry weight.
In a preferred embodiment, the above-mentioned young leaf juice can be obtained by subjecting harvested young leaves of the grass plant or processed products thereof to at least one treatment selected from the group consisting of incubation treatment, anaerobic treatment, and microwave treatment, and squeezing the treated young leaves.
The present invention further provides young leaf juice powder of a grass plant which is at least one selected from the group consisting of barley, wheat, rye, oats, adlay, Italian ryegrass, and rice, containing xcex3-aminobutyric acid in an amount of 800 mg/100 g or more in terms of dry weight.
In a preferred embodiment, the above-mentioned young leaf juice powder can be obtained by subjecting harvested young leaves of the grass plant or processed products thereof to at least one treatment selected from the group consisting of incubation treatment, anaerobic treatment, and microwave treatment, squeezing the treated young leaves, and concentrating, drying, and powdering the juice obtained by the squeezing.
The above-mentioned young leaves, young leaf powder, young leaf juice, and young leaf juice powder of a grass plant are used as materials for food, medicines, or feed.
Thus, the present invention makes possible the objects of: providing young leaves of a grass plant selected from the group consisting of barley, wheat, rye, oats, adlay, Italian ryegrass, and rice, having xcex3-aminobutyric acid, known as an antihypertensive substance, in which the amount of xcex3-aminobutyric acid is enriched or retained, and in which the amount of xcex3-aminobutyric acid is hardly lowered during the steps of processing the leaves or during preservation of the leaves; providing young leaves of a grass plant that have the above-mentioned characteristics and that can retain a vivid green color for a long period of time; and providing young leaf powder, young leaf juice, and young leaf juice powder having the characteristics mentioned above.
The present inventors have intensively examined ingredients naturally contained in green grass leaves and found that the green leaves contain xcex3-aminobutyric acid (GABA), known as an antihypertensive substance. It has also been found that GABA is conventionally lost during the steps of processing green grass leaves, for example, at various stages for producing food materials using green grass leaves. The present inventors have further examined and succeeded in obtaining green grass leaves, especially young leaves of a grass plant selected from barley, wheat, rye, oats, adlay, Italian ryegrass, and rice, which contain retained or increased amount of xcex3-aminobutyric acid, and thus accomplished the present invention.
The young leaves of a grass plant and the young leaf powder of a grass plant included in the present invention contain xcex3-aminobutyric acid in an amount of 500 mg/100 g or more and 20 mg/100 g or more in terms of dry weight, respectively. Both the young leaf juice and young leaf juice powder of a grass plant included in the present invention contain xcex3-aminobutyric acid in an amount of 800 mg/100 g or more in terms of dry weight.
Methods for producing the young leaves of a grass plant, young leaf powder of a grass plant, young leaf juice of a grass plant and young leaf juice powder of a grass plant, each having an increased or retained amount of GABA, are not limited. These products are-produced, for example, by the following methods.
The young leaves of a grass plant having increased or retained amount of GABA can be obtained, for example, by the process of subjecting harvested young leaves of a grass plant or processed products thereof to at least one treatment selected from the group consisting of incubation treatment, anaerobic treatment, and microwave treatment.
As used herein, the term xe2x80x9cgrassxe2x80x9d refers to all the plants belonging to the Gramineae family in the botanical classification. In the present invention, the grass plant is preferably at least one of barley, wheat, rye, oats, adlay, Italian ryegrass, and rice.
The above-mentioned harvested young leaves of a grass plant are young leaves that are preferably harvested prematurely. In more detail, such young leaves are preferably harvested during the period from the start of branching until the early days of earring (when the stem length is about 20 to 40 cm). Young leaves of barley are more preferable.
The harvested young leaves are preferably subjected to the treatment immediately after the harvest. If a time is required before the treatment, the leaves may be stored by a storage means known to those skilled in the art, such as cold storage, for preventing degeneration.
Harvested young leaves may be directly subjected to any of the treatments described above (details to follow). As required, the young leaves are washed with water, preferably 25xc2x0 C. or lower cold water, to remove dirt attached thereto. After being drained, the young leaves are cut into an appropriate length (e.g., 10 cm) as required.
Examples of processed products of young leaves include young leaf fragments and young leaf juice. The young leaf fragments include cut products having a size easy to treat and young leaf slurry.
The cut products are obtained by a method for cutting a plant into pieces generally used by those skilled in the art, such as slicing and shredding. The slurry is obtained by crushing young leaves with a crusher such as a juicer, a mixer, or a blender. By this processing, the young leaves are changed to a thick suspension including liquid and solids having certain fluidity. The young leaf juice is obtained by squeezing young leaves directly or after they have been fragmented. Alternatively, the young leaf juice is obtained by centrifuging or filtering young leaf slurry.
By subjecting the harvested young leaves or processed products thereof to at least one of incubation treatment and anaerobic treatment, the GABA originally contained in the young leaves is enriched.
Incubation treatment may be effected by any appropriate means including heat retaining treatment with the use of hot water, infrared irradiation, and heat retaining treatment with the use of an incubator. The temperature for the incubation treatment is preferably about 20 to 50xc2x0 C., more preferably about 30 to 45xc2x0 C., and most preferably 40xc2x0 C. or around 40xc2x0 C. If the temperature is lower than 20xc2x0 C. or higher than 50xc2x0 C., the increase in GABA content is reduced.
Anaerobic treatment refers to a treatment with (i.e., contact with) a gas containing little oxygen or no oxygen at all, including treatment in the vacuum state. As such a gas, carbon dioxide gas and nitrogen gas are preferably used.
GABA can be sufficiently enriched by being subjected to incubation treatment or anaerobic treatment for ten minutes or longer. Such a treatment is generally continued for 10 minutes to 24 hours, preferably for 1 to 12 hours. With treatment for 30 minutes or longer, the GABA content increases twofold or more. A combination of the incubation treatment and the anaerobic treatment is recommended.
The GABA content of the thus-obtained young leaves is usually higher than that of those subjected to no GABA enriching treatment by twofold or more, preferably threefold or more, more preferably fivefold or more.
By subjecting young leaves of a grass plant or processed products thereof to microwave treatment, the reduction in GABA content during the processing of the young leaves or the reduction in GABA content with time is minimized, whereby the GABA content is retained. GABA may-even be enriched depending on the treatment conditions. By this treatment, not only GABA but also active ingredients such as vitamins (in particular, water-soluble vitamins), minerals, and chlorophyll are retained. In addition, fading of the vivid green color of the leaves and change in flavor are minimized.
In the thus-treated young leaves and processed products thereof, degeneration-related enzymes contained therein are inactivated, which enables the ingredients of the leaves to be retained stably for a prolonged period of time. This also enables the vivid green color to be maintained. When such leaves are used as a health food or a material for health food, the commercial value of the health food is increased.
Microwave treatment may be done with such conditions that degeneration-related enzymes are inactivated and/or the green color is not lost by heating. Such conditions can be appropriately determined by adjusting the microwave wavelength, the output power of a microwave irradiation apparatus, the irradiation time, and the like. In general, the frequency of such a microwave irradiation apparatus is 300 MHz to 30 GHz. The irradiation time is 0.5 to 10 minutes per 100 g (fresh weight, i.e., weight of fresh, undried leaves) of harvested young leaves of a grass plant or processed products thereof (hereinafter, the term xe2x80x9cyoung leaves of a grass plantxe2x80x9d or xe2x80x9cthe young leavesxe2x80x9d may include processed products of the young leaves). For example, when a 2450 MHz, 500 W microwave is used, 100 g (fresh weight) of the young leaves may be subjected to the microwave treatment for 0.5 to 10 minutes, preferably 0.5 to 5 minutes, and more preferably 0.5 to l minute. If the irradiation time is less than 0.5 minutes, the enzymes are only insufficiently inactivated, causing easy color fading of the treated young leaves. Also, ingredients naturally contained in the young leaves tend to be lost. If the irradiation time exceeds 10 minutes, GABA tends to decrease.
The GABA content increases when the microwave treatment time is within about one minute. As the treatment time lengthens, the GABA content decreases. Even if decreasing, however, 80% or more of the GABA content is still retained after a five-minute treatment.
In the above-mentioned method, a recommended procedure for retaining a high GABA content for a prolonged period of time is to use the anaerobic treatment and/or incubation treatment first, followed by the microwave treatment.
The thus-treated young leaves or processed products thereof are used for a desired purpose, for example, as a food material, a medicine material or a feed, directly or after being further processed into an appropriate form. The treated young leaves or processed products thereof are in the form of young leaves, young leaf fragments, young leaf juice, young leaf extract, and the like. The young leaf fragments include cut products having a size easy to treat and young leaf slurry. The extract is obtained by adding a solvent usually used by those skilled in the art, such as water or an ethanol aqueous solution, to the treated young leaves or young leaf fragments and warming as required, to extract active ingredients. The extract includes extract liquid products and concentrated products thereof.
The treated young leaves, young leaf fragments, young leaf juice, and young leaf extract are dried as required. Drying is generally done so that the water content is reduced to 10% or less, preferably 5% or less. In the drying step, the treated young leaves, young leaf fragments, young leaf juice, and young leaf extract, for example, are dried by a method known to those skilled in the art, such as hot air drying, high-pressure steam drying, electromagnetic wave drying, spray drying, and freeze drying. Heat drying is done under such temperature and time conditions that the young leaves will not be discolored due to heating, i.e., preferably at 40 to 80xc2x0 C., more preferably at 55 to 65xc2x0 C. Slurry, extract, and juice of the young leaves may be spray dried with the addition of an excipient such as dextrin, cyclodextrin, starch, or maltose as required.
The resultant dried products may be crushed by a method known to those skilled in the art using, for example, a crusher, mill, blender, stone mill, or the like. The crushed dried young leaves are sifted as required, to obtain, for example, those that have passed through a sieve having a 30 to 250 mesh. If the grain diameter of the crushed pieces is smaller than 250 mesh, further processing is difficult when they are used as a food material or a medicine material. If the grain diameter is larger than 30 mesh, uniform mixing with other food materials is difficult, for example.
The resultant products may be sterilized by a method known to those skilled in the art, such as air current sterilization, high pressure sterilization, and heating sterilization.
In the thus-treated young leaves or processed products thereof, the GABA content has been increased, or the high GABA content has been retained through the processing. The GABA content has usually been increased twofold or more, preferably threefold or more, and more preferably fivefold or more, compared with that of young leaves that were not treated by the method of the present invention.
For example, young leaves of a grass plant selected from barley, wheat, rye, oats, adlay, Italian ryegrass, and rice subjected to the GABA enriching treatment (anaerobic treatment and/or incubation treatment) contain GABA in an amount of at least 100 mg/100 g (based on fresh weight of leaves; 500 mg/100 g in terms of dry weight), usually 150 to 200 mg/100 g, preferably 300 mg/100 g or more, and more preferably 500 mg/100 g or more. The GABA content in just harvested young leaves is 80 mg/100 g at most. Therefore, the GABA content increases roughly twofold or more.
Young leaf powder of a grass plant selected from barley, wheat, rye, oats, adlay, Italian ryegrass, and rice produced through the microwave treatment, but not through the GABA enriching treatment, contains GABA in an amount of at least 20 mg/100 g (based on dry weight), usually 100 mg/100 g or more, preferably 200 mg/100 g or more, and more preferably 500 mg/100 g or more. Young leaf powder of the same plant produced through the GABA enriching treatment contains GABA in an amount of at least 50 mg/100 g (based on dry weight), usually 200 mg/100 g or more, preferably 500 mg/100 g or more, more preferably 1000 mg/100 g or more. For reference, the GABA content in young leaf powder of the same plant produced through the conventional hydrothermal treatment (i.e., blanching) is 10 mg/100 g (based on dry weight) at most.
Young leaf juice of a grass plant selected from barley, wheat, rye, oats, adlay, Italian ryegrass, and rice produced through the microwave treatment, but not through the GABA enriching treatment, contains the GABA in an amount of at least 10 mg/100 g (Value in liquid weight; 400 mg/100 g in terms of dry weight), usually 20 mg/100 g or more, preferably 30 mg/100 g or more, and more preferably 50 mg/100 g or more.
Young leaf juice of the same plant produced through the GABA enriching treatment contains GABA in an amount of at least 20 mg/100 g (value in liquid weight; 800 mg/100 g in terms of dry weight), usually 30 mg/100 g or more, preferably 50 mg/100 g or more, and more preferably 100 mg/100 g or more. For reference, the GABA content in young leaf juice of the same plant produced through the conventional hydrothermal treatment is 2 mg/100 g (value in liquid weight) or less.
Young leaf juice powder of a grass plant selected from barley, wheat, rye, oats, adlay, Italian ryegrass, and rice, produced through the microwave treatment, but not through the GABA enriching treatment, contains GABA in an amount of at least 400 mg/100g (based on dry weight), usually 800 mg/100 g or more, preferably 1200 mg/100 g or more, and more preferably 1600 mg/100 g or more. Young leaf juice powder of the same plant produced through the GABA enriching treatment contains GABA in an amount of at least 800 mg/100 g (based Ion dry weight), usually 1200 mg/100 g or more, preferably 2000 mg/100g or more, and more preferably 4000 mg/100 g or more. For reference, the GABA content in young leaf juice powder of the same plant produced through the conventional hydrothermal treatment is 80 mg/100 g (dry weight) at most.
The young leaves of the grass plant or processed products thereof subjected to the above method to retain or increase the GABA content are also rich in active ingredients such as vitamins, minerals, and chlorophyll, compared with those obtained by conventional hot water blanching. For example, young leaf powder of a grass plant selected from barley, wheat, rye, oats, adlay, Italian ryegrass, and rice obtained according to the present invention contains: carotene usually twofold or more, preferably fivefold or more; vitamin B1 usually fivefold or more, preferably tenfold or more; vitamin C usually 100-fold or more, preferably 200-fold or more; calcium usually twofold or more, preferably fivefold or more; potassium usually twofold or more, preferably fivefold or more; and chlorophyll usually twofold or more, preferably fivefold or more, compared with those obtained by the conventional method. In addition, since the vivid green color of the young leaves can be maintained through the treatment and also after the treatment, the value as a health food and a material for health food, for example, is high.
The young leaves or processed products thereof with the retained or increased GABA content can be used as materials for foods, drinks, medicines, and a feed directly or by being mixed with an excipient, an extender, a binder, a thickener, an emulsifier, a colorant, a perfume, a food additive, a seasoning, and the like. For example, royal jelly, vitamins, proteins, calcium compounds, chitosan, lecithin, and the like may be mixed, and syrup and a seasoning may be added to correct the taste. The resultant products may be formed into capsules such as hard capsules and soft capsules, tablets, or pills, or otherwise in the shapes of powder, granules, tea leaves, tea bags, candy bars, or the like. These products may be ingested as they are, or dissolved in cold water, hot water, or milk for drinking. Otherwise, their ingredients may be leached out and ingested. The thus-obtained young leaves of a grass plant or processed products thereof may also be added to feed for animals such as livestock and pets.
Thus, according to the present invention, the young leaves containing GABA at a high concentration are obtained. Thus, a pure GABA product can also be obtained from the young leaves.